Sue Rice got a shock when she opened her daughter's nursery yearbook to see the photograph of the smiling four-year-olds. Their eyes had been blacked out. Sue is one of a group of parents affected by a de facto photography ban at their primary school in a quiet area of Hertfordshire. It started with a notice in the school newsletter saying that no photography was permitted at the nativity play, but that parents could buy a DVD for £12.

Requests to take pictures had to be made in writing to the headteacher, but in almost all cases were refused "due to the safeguarding of all children". In spite of repeatedly taking the issue up with the school and governing body, these parents have been denied photographs of their children at sports days and Christmas plays – even at the PTA craft fair.

Such a blanket ban is relatively rare, but the issue of photographing children has become fraught in schools all over Britain. Ten years ago, nobody thought twice about photographing children on the football field. Now every click of the camera is overhung with a cloud of possible ill intent. Who is photographing that child and why? What will they do with the photo? The epitome of innocence – parents recording their child's nativity play – has become subject to the strictest regulation.

The Hertfordshire primary school's lengthy 2008 photography policy read like a particularly thorny piece of contract law. "Parents just couldn't understand it," says Monica, another mother at the school, which has now shortened the policy to four pages although photography is still banned.

Many schools and sports groups have both parental and children's consent forms, and if parents want to take pictures themselves they must also fill in a "camera registration" form, after which they will be issued with an armband or sticker. Three forms, to take a photograph.

Rules governing the storage of photos of school football are becoming stricter than, say, rules governing the police storage of DNA. Robin Hood primary and nursery school in Nottinghamshire says its photographs are stored in a "secure location" for not more than four years, after which they are "privately destroyed".

A secondary school teacher from Hertfordshire, who wishes to remain anonymous, says that he was only allowed to photograph his own school's pupils at sports events, so "if there are three kids on a medal platform, you have to take your child away from the platform and photograph them separately".

The Child Protection in Sport Unit recommends that you "avoid full-face and body shots" and that children in swimming costumes should only be shown "from waist or shoulder up". These rules create a stilted genre of child photography, where children are pictured on their own or at designated "photo moments" at the end of the play or match, rather than in the thick of events.

Schools often invoke the Data Protection Act 1998, or the Children Act 2004 as the reason for photography bans. "But there is nothing in the Children Act that says 'Thou shalt not photograph children'," says Eleanor Coner, information officer at the Scottish Parent Teacher Council. The Information Commissioner's Office has taken to putting out bi-annual statements refuting the myth that the Data Protection Act prohibits photography. "We call it the 'data protection duckout'," says David Smith, director of data protection at the Information Commissioner's Office. "If there is something people don't want to do, but they can't explain it easily, they say it's because of the Data Protection Act."

In fact, photography bans cannot be traced to any single event or law. Rather, it seems that there was a shift from the early 2000s, when similar regulations diffused throughout schools and sports organisations.

The first widely reported ban was a Yorkshire primary school in 1999, followed by Perth and Kinross council in 2000 and Edinburgh District Council in 2002. The Amateur Swimming Association first drew up a photography policy in 1999 and the Child Protection in Sport Unit published a similar document in 2002, which then spread through sports governing bodies.

Some schools and clubs are more liberal, but these are increasingly rare. When I contacted a number of UK sporting associations, only one (shooting) lacked significant restrictions.

As an example of how attitudes have changed, a manufacturer of children's play equipment asked a photographer, John Robertson, to photograph its apparatus at a variety of English sites: he was shouted at and parents snatched away their children in parks in Nottingham, Cambridge and the Isle of Wight.

The spread of photo bans is not really a response to child abusers stalking school sports days. Instead, it reflects the contamination of everyday adult-child relations – and the new assumption, as the children's author Philip Pullman put it, that "the default position of one human being to another is predatory rather than kindness". Any adult looking through the viewfinder at a child is viewed as potentially sinister and in need of regulation.

Of course, none of these restrictions would stop a paedophile getting hold of images of children; and apart from anything else it would be easy enough to pay £12 for a school nativity DVD or, indeed, register their camera.

It is not the child abuser but the loving parent who suffers from these rules. "You miss out on the milestones in your child's life," says Sue Rice. "It is a shame because they are small for such a short time."

David Smith from the Information Commissioner's Office makes the sensible suggestion that "if there are strangers acting in a strange manner at a sports day, you would expect the school to challenge them", but parents snapping their children running races on sports day should not be an issue.

Photography validates children's experiences and achievements, and they hang a lot on the image of them scoring the winning goal or receiving the trophy. Eleanor Coner says that photographs of their peers are important too: "It is no good when parents are only allowed to photograph their own child. This is a record of their school life. Parents need to be able to photograph all the sheep and the baby Jesus."

Indeed – let the nativity be an innocent scene once again.

• Some names have been changed. Josie Appleton is the director of the civil liberties group the Manifesto Club, manifestoclub.com